Support for browser extensions

[dmarti]

To help address concerns about possible side effects of FLoC (see issue 16), please help facilitate independent research by making the FLoC Key available for browser extensions to get and set.

The FLoC README states,

Flocks could be evaluated for fairness by measuring and limiting their deviation from population-level demographics with respect to the prevalence of sensitive categories, to prevent their use as proxies for a sensitive category. However, this evaluation would require knowing how many individual people in each flock were in the sensitive categories, information which could be difficult or intrusive to obtain.

That kind of data collection would be impractical to get consent for in general, but there is an exception. Some browser users choose to participate in NGO-led research to share information about advertising practices that affect them. The best-known example is Ad Observer - Chrome Web Store, previously Facebook Political Ad Collector.

Facilitating this kind of independent research by volunteer, opt-in browser users would be a valuable step to address concerns about discriminatory side effects of FLoC. For example, volunteers could run a research extension to gather data to help address the question: do people get different ads for jobs and housing when browsing in a flock related to assistive technology and in a flock related to some other technical interest?

[AramZS]

I support this idea. I think it could also be helpful for those interested in providing specialized UIs to aid browser users in understanding what their membership in a FLoC means, what the FLoC means and removing themselves from a FLoC. While I assume that the browser will provide users with tools to make informed choices about FLoC and individual FLoC measurement, there may be better tools provided by interested parties with an investment in helping users exit or avoid specific cohorts, or otherwise handle their privacy concerns.

[dmarti]

Ad Topics Hints is a possible use case for extension-supplied cohorts.

One possible approach would be to make this API “pluggable”. Such browser plugins would need to be reviewed / vetted to ensure user privacy and stop abuse. Plugins would have access to the ad-interaction data described in the “sensible defaults” section as well as user feedback on ads, and could design their own user-interfaces as well as algorithms to generate the “Ad Topic Hints” returned.

An extension could return the ad topics hints as the cohort id, with an alternate version to specify the ad topics hints algorithm used.

[michaelkleber]

It seems like this would be easy if the extension were to be responsible for everything. I'm not sure how we could split the work up so that the browser still ensured privacy properties while the extension got to work on variants like you suggest.

[dmarti]

The extension may end up with a set of privacy properties different from the browser defaults. Different users have different sets of preferences regarding willingness to trade information for personalization. The browser extension store, or the extension installation workflow, would have to make it clear to the user that they are installing an extension that changes the privacy characteristics of the browser in some way. Browser extensions can already compromise the user's information in other ways, so this would not create a new area of responsibility for the operators of browser extension stores.

A single in-browser set of privacy properties puts the Web at a disadvantage for either the privacy-sensitive users or for the users who are willing to trade information for personalization. In the future it should be possible for a browser to discover and auto-customize its behavior, based whether it is acting as the user agent of a privacy person or a personalizer, and no extension would be needed. For now, though, the Ad Topics Hints issue linked above suggests that extensions are a way to enable research and competition between alternatives.